Abstract PD8-11: Distribution of locoregional breast cancer recurrences in relation to previous radiotherapy and biological subtype

Background: Adjuvant locoregional radiotherapy (LRRT) reduces risk of locoregional failures (LRF) and improves survival for node positive breast cancer (BC) patients. However, LRRT increases the risk for toxicity as edema in the arm, lung cancer and cardiac mortality. Modern radiotherapy allows a more conform therapy which makes knowledge of LRF-patterns very important, in order not to underdose volumes with high risk for microscopic disease and simultaneously restrict dose to risk organs. In addition, BC-subtype may affect radiosensitivity and could possibly be used to individualize LRRT in the future.

Methods: We investigated outcome for BC-patients receiving LRRT in the Southwest Sweden (2004-2008) in order to identify LRFs. During this period patients with >3 positive lymph nodes were given LRRT (50Gy in 2Gy fractions) to the breast/thoracic wall, axilla level II+III, supra- and infraclavicular lymph nodes according to a target definition atlas introduced in 2002. Patients with LRF as first event were identified, with distant failures and death considered as competing risks. The anatomical distribution of LRF was compared with the contouring atlas, radiotherapy given, and biological subtype based on immunohistochemistry.

Results: 904 patients received LRRT. Median follow-up time was 9.8 years (0.2-14.6) for patients without an event. 59 patients (6,5%) developed a LRF, 30 of which were local failures (LF) and 31 regional failures (RF) (2 simultaneous LF/RF). Median time to LRF was 2.8 years. 37 of the 59 (63%) LRF-patients developed generalized disease within 3 months from the LRF. Of the 845 patients without LRF 316 developed distant metastases as first recurrence, 1 an isolated RF in the contralateral axilla, 64 died from other causes, and for 5 patients recurrence-status was unclear. 459 were alive at end of follow-up.

Of the LF 19 developed after mastectomy (MRM) and 11 after breast conserving surgery (BCS). LF-location after MRM: 9 in-field, 6 at field margin, 2 both in/out of field, 1 out of field, and for 1 not yet determined. After BCS: 8 in-field, 1 at field margin, and for 2 not yet determined. Of the RF 28 developed after MRM and 3 after BCS. Location of RF after MRM: 11 in-field, 6 at field margin, 1 both in/out of field, 2 out of field, and for 8 not yet determined. After BCS: 1 in-field, 1 at field margin, and 1 not yet determined. The most common location for RF close to /out of field was superior to the treated area in fossa supraclavicularis.

Biological approximate subtype was available for 885 of the primary tumours; luminal (ER+ and/or PR+ HER2-/?) 67% (589/885), HER2+ 19% (169/885), triple negative (ER- and PR- HER2-/?) (TN) 14% (127/885). Subtype distribution of BC later causing LRF despite LRRT was: luminal 44% (26/59), HER2+ 27% (16/59), TN 29% (17/59). Among primary tumours causing a LRF within irradiated volume 77% (24/31) were HER2+ or TN.

Conclusion: In this high risk cohort of BC-patients, we found a low incidence of LRFs. The majority of LRFs developed within irradiated volume. BCs of the HER2+ and TN-subtype may be more radioresistant and have a higher risk of LRF. Updated information as well as figures mapping all recurrences in relation to previous LRRT will be presented at the symposium.

Citation Format: Adra J, Karlsson P, Killander F, Lundstedt D, Alkner S. Distribution of locoregional breast cancer recurrences in relation to previous radiotherapy and biological subtype [abstract]. In: Proceedings of the 2018 San Antonio Breast Cancer Symposium; 2018 Dec 4-8; San Antonio, TX. Philadelphia (PA): AACR; Cancer Res 2019;79(4 Suppl):Abstract nr PD8-11.

Abstract P1-10-05: Omitting radiotherapy in women ≥ 65 years with early breast cancer and favorable histopathology after breast-conserving surgery, sentinel node biopsy and adjuvant endocrine therapy is safe

Background: The benefit of radiotherapy in older women with endocrine responsive early breast cancer treated with breast-conserving surgery and endocrine therapy is unclear. The aim of this study was to verify if omission of radiotherapy in a predefined cohort of patients with good prognosis early breast cancer after breast conservation is safe.

Methods: Eligibility criteria were: consecutive patients with age ≥ 65 years, breast-conserving surgery (sector resection + sentinel node biopsy), clear margins, unifocal T 1 N0, Elston grade 1 and 2, estrogen receptor-positive. After informed consent adjuvant endocrine therapy, either tamoxifen or an aromatase inhibitor, was prescribed for 5 years. Primary endpoint was ipsilateral breast tumor recurrence (IBTR). Secondary endpoints were contralateral breast cancer, recurrence-free survival (RFS) and overall survival (OS).

Results: Between 2006 and 2012, we included 603 women from 14 Swedish centers. Two patients did not fulfill the inclusion criteria and were excluded from the analysis. Median age was 71 years (range 65 to 90). At a median follow-up of 59 months (range 2 to 110) 13 IBTR (cumulative incidence at five years, 1.3% (95% CI, 0.6% to 2.7%), 4 regional recurrences (one combined with IBTR), 2 distant recurrences both without IBTR or regional recurrence and 11 contralateral breast cancers was observed. Twenty-nine patients were diagnosed with tumors of other origin. Seven of them were endometrial cancers. There were 39 deaths. Only one of the deaths (2.6%) was due to breast cancer and 11 (28.2%) were due to other cancers (2 endometrial cancers). Five-year overall survival was 93.9% (95% CI, 91.4% to 95.7%).

Conclusion: This study demonstrates, with a median follow-up of 59 months, that breast-conserving surgery and endocrine therapy without radiotherapy is a safe treatment option in women with early breast cancer and favorable histopathology aged ≥ 65 years. The risk of IBTR is comparable to the risk of contralateral breast cancer. The low rate of breast cancer deaths indicates that breast cancer mortality is of secondary importance in this subset of women.

Citation Format: Villman KKA, Wickberg Å, Killander F, Lindman H, Bjöhle J, Edlund P, Tennvall-Nittby L, Bachmeier K, Carlberg M, Blomqvist C, Ahlgren J, Liljegren G. Omitting radiotherapy in women ≥ 65 years with early breast cancer and favorable histopathology after breast-conserving surgery, sentinel node biopsy and adjuvant endocrine therapy is safe [abstract]. In: Proceedings of the 2016 San Antonio Breast Cancer Symposium; 2016 Dec 6-10; San Antonio, TX. Philadelphia (PA): AACR; Cancer Res 2017;77(4 Suppl):Abstract nr P1-10-05.

No breast cancer subgroup can be spared postoperative radiotherapy after breast-conserving surgery. Fifteen-year results from the Swedish Breast Cancer Group randomised trial, SweBCG 91 RT

BACKGROUND

Breast-conserving surgery (BCS) followed by radiotherapy (RT) is an established treatment for women with T1-2N0 breast cancers. Since subgroups of patients have low ipsilateral breast tumour recurrence (IBTR) rates, it is important to study whether RT is necessary for all patients.

PATIENTS AND METHODS

A total of 1187 women with primary T1-2N0M0 breast cancer were randomised, after standardised sector resection, to postoperative whole breast RT or no local treatment. Adjuvant systemic therapy was offered to patients with stage II cancers. Patients were followed with clinical examinations and annual mammography for 10 years and thereafter referred to the Swedish mammography screening program.

RESULTS

After 15 years of follow-up, a higher cumulative incidence of IBTR was observed in control patients, 23.9%, versus irradiated patients, 11.5%, P<0.001. Recurrence-free survival was inferior, 51.7% versus 60.4%, P=0.0013. The main effect of RT was seen during the first 5 years. However, overall survival was not significantly lower 68.4% versus 71.1%, P=0.68, nor was breast cancer-specific mortality significantly higher.

CONCLUSIONS

RT after BCS significantly reduced the incidence of IBTR at 15 years of follow-up. We were unable to identify subgroups which could be spared RT. Breast cancer mortality was not significantly reduced after RT. Good predictive markers for radiation sensitivity and improved adjuvant systemic therapy are needed to omit RT after BCS.

No positive effect of postmastectomy radiotherapy on mortality at 20 years in pre menopausal women with stage II breast cancer also treated with adjuvant oral cyclophopsphamide. South Sweden Breast Cancer Group, trial SBII:I

Abstract #5128

Purpose: To study long term loco-regional recurrence rate and survival after postmastectomy radiotherapy in combination with oral cyclophosphamide in premenopausal women with stage II breast cancer.&#x2028; Study design: A three-armed randomised, multicenter, phase III trial comparing 1) Radiotherapy (RT) 2) RT+ oral cyclophosphamide for one year (RT+C) and 3) cyclophosphamide only (C).&#x2028; Radiotherapy was administered with 48 Gy in 20 fractions to chest wall and locoregional lymph nodes (Arwidi Å, Acta Oncol Scand 18:273-281, 1979). Cyclophosphamide was prescribed as 12 courses of 130 mg/m2 od for14 days every 4 weeks.&#x2028; Patients and methods: 367 patients from 15 departments in Southern Sweden, representing 80% of all eligible patients, were included in the trial between 1978-1983; n=124 (RT), n=118 (RT+C), n=125 (C). Median age was 47 years, median tumour size was 25 mm, and 33 % of the patients were lymph node negative. Median follow up for survival was 24 years and 21 years for other events.&#x2028; Results: RT reduced the risk at twenty years for locoregional recurrence in C treated patients with 75 %, 13.9 vs 3.5 %. The risk reduction was highly significant in both N0 and N+ patients. RT did not decrease systemic disease or mortality, see table 1. Chemotherapy did not decrease mortality when added to radiotherapy, though difficult to evaluate because of lack of information on delivered doses in many cases.&#x2028; &#x2028; Conclusion: Postmastectomy radiotherapy reduces loco regional recurrences in this premenopausal population, but no effect was seen on mortality at 20 years. Possible explanations are 1) low number of loco regional recurrences and superior survival in comparison to other trials investigating postmastectomy radiotherapy, which might have modified the effect of RT on survival, 2) too low intensity of adjuvant, single agent chemotherapy, and 3) chance, since relatively small study with little power.

Citation Information: Cancer Res 2009;69(2 Suppl):Abstract nr 5128.

Elevation of ADP-ribosylation as an indicator of mononuclear leucocyte responsiveness in breast cancer patients treated with tamoxifen

82 women who had had surgery for removal of breast cancer were randomised during the primary care period before initiation of any chemotherapy or radiotherapy into two groups: no drug treatment (n = 40) and 20 mg tamoxifen per day for 2 years (n = 42). Mononuclear leucocyte (MNL) fractions from blood samples were collected during the first 368 days of the study and ADP-ribosylation was quantified. Tamoxifen treatment resulted in a dose-duration increase in ADP-ribosylation. This was true even after adjustment for covariates such as age, smoking habits, oestrogen use, menstruation and tumour size. These data suggest that part of the antitumour effects of tamoxifen treatment in vivo relates to an enhanced immune cell responsiveness, as indicated by the increased MNL ADP-ribosylation.